Renal Failure: AKI vs CKD, Fluid/Electrolyte Management, Dialysis

Renal Failure: AKI vs CKD, Fluid/Electrolyte Management, Dialysis

A practical guide for nurses, clinicians, and medical learners.

What Is This?

Renal failure occurs when kidneys lose their ability to filter waste, regulate fluids, and balance electrolytes. This guide distinguishes acute kidney injury (AKI) from chronic kidney disease (CKD), explains fluid/electrolyte management, and covers dialysis principles—critical for patient stabilization and long-term care.

Why use this today? - AKI affects 1 in 5 hospitalized patients, with mortality rates >50% in severe cases. - CKD impacts 10% of the global population, requiring lifelong management. - Dialysis sustains ~3 million people worldwide, but complications (e.g., hypotension, infections) demand precise interventions.

Why It Matters

• AKI: Rapid onset, often reversible, but missed diagnoses lead to permanent damage.
• CKD: Progressive, irreversible, and a major risk factor for cardiovascular disease.
• Fluid/electrolyte imbalances (e.g., hyperkalemia, metabolic acidosis) can cause fatal arrhythmias or seizures.
• Dialysis is life-saving but requires vigilant monitoring to prevent complications like disequilibrium syndrome or access site infections.

Real-world impact: - Hospitals: AKI increases ICU stays by 3–5 days and costs by $10,000–$40,000 per episode. - Outpatient: CKD patients on dialysis spend 12+ hours/week in treatment, with 20% annual mortality. - Public health: CKD is the 9th leading cause of death in the U.S.; early intervention reduces progression to end-stage renal disease (ESRD).

Core Concepts

1. AKI vs CKD: Key Differences

Key takeaway: - AKI = Emergency. Focus on volume resuscitation, avoiding nephrotoxins, and identifying the cause (prerenal, intrarenal, postrenal). - CKD = Long-term management. Prioritize BP control, glycemic management, and dialysis planning.

2. Fluid & Electrolyte Management

Fluid Balance

• AKI: Often hypovolemic (prerenal) or hypervolemic (intrinsic/postrenal).
• Hypovolemia: Give IV fluids (NS or LR) to restore perfusion.
• Hypervolemia: Use diuretics (furosemide) or dialysis if refractory.
• CKD: Fluid restriction (1–1.5 L/day) to prevent pulmonary edema.

Electrolyte Imbalances

Critical alerts: - K? > 6.0 mEq/L-Emergency. Give calcium gluconate (stabilizes cardiac membrane), then insulin + glucose (shifts K? into cells). - Na? < 120 mEq/L-Seizure risk. Correct slowly to avoid osmotic demyelination syndrome.

3. Dialysis: Principles & Modalities

When to Dialyze (AEIOU Mnemonic)

• Acid-base imbalance (metabolic acidosis, pH < 7.1)
• Electrolyte emergencies (K? > 6.5 mEq/L)
• Intoxications (lithium, ethylene glycol)
• Overload (pulmonary edema unresponsive to diuretics)
• Uremia (pericarditis, encephalopathy, BUN > 100 mg/dL)

Dialysis Modalities

Key nursing actions: - HD: Monitor for hypotension (give NS bolus), access site bleeding (hold pressure), disequilibrium syndrome (slow rate if headache/nausea). - PD: Check for cloudy effluent (peritonitis), hernias (from fluid pressure). - CRRT: Assess filter clotting (check ACT/PTT), hypothermia (use blood warmer).

Hands-On: Step-by-Step Management

1. AKI Workup & Intervention

Prerequisites: - Basic lab skills (BMP, ABG, urinalysis). - IV access (peripheral or central line).

Steps:
1. Assess volume status: - Hypovolemic?-Give 500–1000 mL NS bolus over 30 mins. - Hypervolemic?-Furosemide 40–80 mg IV (if urine output present).
2. Check labs: - Creatinine rise > 0.3 mg/dL in 48h-AKI. - Urine Na? < 20 mEq/L-Prerenal (give fluids). - Urine Na? > 40 mEq/L-Intrinsic (stop nephrotoxins).
3. Avoid nephrotoxins: - Hold NSAIDs, ACEi/ARBs, contrast dye, aminoglycosides.
4. Monitor urine output: - < 0.5 mL/kg/h for 6h-Stage 1 AKI (notify MD).

Expected outcome: - Urine output improves within 6–12h if prerenal. - Creatinine stabilizes in 24–48h if cause removed.

2. CKD: Slowing Progression

Prerequisites: - BP cuff, glucometer, phosphate binders.

Steps:
1. Control BP: - Target < 130/80 mmHg (use ACEi/ARB unless contraindicated).
2. Manage diabetes: - HbA1c < 7% (avoid metformin if GFR < 30).
3. Dietary modifications: - Protein: 0.6–0.8 g/kg/day (avoid excess). - Potassium: < 2 g/day (avoid bananas, potatoes). - Phosphate: < 800 mg/day (take binders with meals).
4. Prepare for dialysis: - GFR < 20 mL/min-Refer to nephrology. - AV fistula (preferred) or catheter (temporary).

Expected outcome: - GFR decline < 1 mL/min/year (vs. 4–5 mL/min/year without intervention).

3. Hyperkalemia Emergency Protocol

Prerequisites: - Cardiac monitor, IV access, insulin/glucose, kayexalate.

Steps:
1. Stabilize cardiac membrane: - Calcium gluconate 1 g IV over 2–3 mins (repeat if ECG changes persist).
2. Shift K? into cells: - Insulin 10 units IV + 50 mL D50W (monitor glucose). - Albuterol 10–20 mg nebulized (additive effect).
3. Remove K? from body: - Kayexalate 15–30 g PO/PR (onset 1–2h). - Dialysis if K? > 6.5 mEq/L and refractory.
4. Monitor: - Repeat K? in 1h (goal < 5.5 mEq/L). - ECG (peaked T waves-widened QRS-sine wave-arrest).

Expected outcome: - K? drops 0.5–1.0 mEq/L within 1h; normalizes in 4–6h.

Common Pitfalls & Mistakes

1. Overcorrecting hyponatremia:
2. Mistake: Giving 3% saline too fast-osmotic demyelination.

3. Fix: Raise Na? < 8–10 mEq/L in 24h.

4. Ignoring urine output in AKI:

5. Mistake: Assuming normal creatinine = no AKI.

6. Fix: Urine output < 0.5 mL/kg/h for 6h = AKI (even if creatinine is normal).

7. Using ACEi/ARBs in AKI:

8. Mistake: Continuing lisinopril in prerenal AKI-worsens hypoperfusion.

9. Fix: Hold ACEi/ARBs if creatinine rises > 30%.

10. Delaying dialysis in uremia:

11. Mistake: Waiting for "perfect" timing-pericarditis or encephalopathy.

12. Fix: Dialyze if BUN > 100 mg/dL or symptomatic uremia (nausea, asterixis).

13. Overlooking PD peritonitis:

14. Mistake: Assuming cloudy effluent is "normal."
15. Fix: Send fluid for cell count/culture (WBC > 100/mm³ = peritonitis).

Best Practices

AKI Prevention

• Hydrate before contrast studies (NS 1 mL/kg/h for 12h pre/post).
• Avoid nephrotoxins (check meds: NSAIDs, aminoglycosides, vancomycin).
• Monitor urine output in high-risk patients (sepsis, post-op, heart failure).

CKD Management

• BP control: ACEi/ARB first-line (unless hyperkalemic).
• Diet: Low potassium/phosphate; avoid salt substitutes (high in K?).
• Vaccines: Annual flu, pneumococcal, hepatitis B (if dialysis candidate).

Dialysis Care

• HD: Prime lines with NS to prevent air embolism; check access thrill/bruit daily.
• PD: Sterile technique for exchanges; warm dialysate to body temp.
• CRRT: Anticoagulate (heparin/citrate) to prevent filter clotting.

Tools & Frameworks

Real-World Use Cases

1. Post-Op AKI in Cardiac Surgery
2. Scenario: Patient develops oliguria (20 mL/h) 12h post-CABG.

3. Action:

   • Check FENa (prerenal vs. intrinsic).
   • Give 500 mL NS bolus (if hypovolemic).
   • Hold furosemide (worsens prerenal AKI).
   • Start CRRT if hyperkalemic or acidotic.

4. CKD Progression in Diabetes

5. Scenario: Patient with HbA1c 9.2%, GFR 45 mL/min, BP 150/90.

6. Action:

   • Start lisinopril 10 mg daily (BP + renal protection).
   • Refer to endocrinology for insulin adjustment.
   • Educate on low-K? diet (avoid tomatoes, oranges).

7. Hyperkalemia in ESRD

8. Scenario: Dialysis patient presents with K? 7.2 mEq/L, peaked T waves.
9. Action:
   • Calcium gluconate 1 g IV (stabilize heart).
   • Insulin 10 units + D50W (shift K? into cells).
   • Emergent HD (remove K?).

Check Your Understanding (MCQs)

Question 1

A 65-year-old man with CKD stage 4 (GFR 22 mL/min) presents with BP 160/95 mmHg. His current meds include metformin, lisinopril, and furosemide. Which intervention is most appropriate?

A. Increase lisinopril to 20 mg daily B. Add amlodipine 5 mg daily C. Stop metformin and start glipizide D. Increase furosemide to 80 mg daily

Correct Answer: C - Why: Metformin is contraindicated in GFR < 30 (risk of lactic acidosis). Glipizide is safer in CKD. - Distractors: - A: Lisinopril is renal-protective but may worsen hyperkalemia in CKD. - B: Amlodipine is a good add-on but doesn’t address the metformin risk. - D: Furosemide may help BP but doesn’t address the primary issue (metformin).

Question 2

A patient in the ICU with AKI has K? 6.8 mEq/L,